@article{IM_1984__76_143129,
     author = {U. Oertel},
     title = {Incompressible branched surfaces.},
     journal = {Inventiones mathematicae},
     pages = {385--410},
     publisher = {mathdoc},
     volume = {76},
     year = {1984},
     zbl = {0539.57006},
     url = {http://geodesic.mathdoc.fr/item/IM_1984__76_143129/}
}